Monte Carlo Simulation Of Magnetorheological Fluid Phase Separation

As a new type of smart material with sensitive reaction on external magnetic induction, magnetorheological fluid (hereafter referred to as MRF) has excellent controllable property. MRF can be made by adding some magnetic particles into non-magnetic base fluid together with different kinds of additives so as to improve performance. Without external magnetic induction, MRF is embodied in the state of Newtonian fluid. However, when a certain external magnetic field is imposed on it, it would convert to a solid-like in seconds. Moreover, when affected by external magnetic induction, it would gain a good capacity of shear yield resistance, This newly gained capacity would change along with the strength of external magnetic induction and it is easy to control and adjust within a wide range of working temperature. Therefore, the current application of MRF is of extensive prospect and MRF as well as many MRF-related devices can be seen in various areas.This thesis mainly focuses on the study of magnetorheological effect theory and intends to simulate liquid-solid phase separation according to Monte Carlo simulations.(1 introducing the composition and structure of MRF, the physical mechanism, preparation methods, etc. Only when the material is deeply studied from all aspects, can we accurately figure out its phase separation.(2)The plate type is supposed to be used in this study to calculate under different conditions the strength of the magnetic dipole interaction energy generated by (NPT and NVT) uniform particles and two differently sized particles under magnetic induction in the vertical direction between plates as well as rotating magnetic induction. This thesis will establish a dipole interaction model, and deduce calculation of interaction energy between NVT magnetic dipoles through the Ewald sum method.(3)Writing a program by Fortran language on interaction energy between magnetic dipoles in MRF; Calculating in Fortran Powr Station 4.0 software and simulating with Monte Carlo method; Figuring out a low-energy state of extreme value and set it as an equilibrium state of the system; Analyzing magnetic particles aggregation in the equilibrium state and studying the physical mechanism of phase separation of magnetic particles.(4)In the case of NVT canonical ensemble, the magneto-rheological fluid in an axial magnetic field is strong enough, the magnetic particles will form a tight chain structure, when a larger axial magnetic field, the magnetic particles form columnar structure, the average the lowest energy particles; when its subjected to a rotating magnetic field, the magnetic particles form a layered structure. In this case, the volume fraction of particles greater impact on the phase separation, the volume fraction of the larger particles are aggregated more closely, the lower the average energy per particle.(5)In the case of NPT ensemble, the same, magneto-rheological fluid in an axial magnetic field is strong enough, the magnetic particles will form a tight chain structure, when a larger axial magnetic field, the magnetic particles form columnar structure, the average each lowest energy particles; when its subjected to a rotating magnetic field, the magnetic particles form a layered structure. Factors affecting the phase separation include:volume fraction of the magnetic field strength, pressure, etc., but in this case, and the influence of the pressure influence and the magnetic field strength is also important, when the greater the pressure, the more compact pellets, per the lower the energy of a particle.